// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_WORLD_CALLBACKS_H
#define B2_WORLD_CALLBACKS_H

#include "b2_api.h"
#include "b2_settings.h"

struct b2Vec2;
struct b2Transform;
class b2Fixture;
class b2Body;
class b2Joint;
class b2Contact;
struct b2ContactResult;
struct b2Manifold;

class b2ParticleSystem;
class b2ParticleGroup;
struct b2ParticleBodyContact;
struct b2ParticleContact;

/// Joints and fixtures are destroyed when their associated
/// body is destroyed. Implement this listener so that you
/// may nullify references to these joints and shapes.
class B2_API b2DestructionListener
{
public:
  virtual ~b2DestructionListener() {}

  /// Called when any joint is about to be destroyed due
  /// to the destruction of one of its attached bodies.
  virtual void SayGoodbye(b2Joint* joint) = 0;

  /// Called when any fixture is about to be destroyed due
  /// to the destruction of its parent body.
  virtual void SayGoodbye(b2Fixture* fixture) = 0;
  
  /// Called when any particle group is about to be destroyed.
  virtual void SayGoodbye(b2ParticleGroup* group)
  {
    B2_NOT_USED(group);
  }
  
  /// Called when a particle is about to be destroyed.
  /// The index can be used in conjunction with
  /// b2ParticleSystem::GetUserDataBuffer() or
  /// b2ParticleSystem::GetParticleHandleFromIndex() to determine which
  /// particle has been destroyed.
  virtual void SayGoodbye(b2ParticleSystem* particleSystem, int32 index)
  {
    B2_NOT_USED(particleSystem);
    B2_NOT_USED(index);
  }
};

/// Implement this class to provide collision filtering. In other words, you can implement
/// this class if you want finer control over contact creation.
class B2_API b2ContactFilter
{
public:
  virtual ~b2ContactFilter() {}

  /// Return true if contact calculations should be performed between these two shapes.
  /// @warning for performance reasons this is only called when the AABBs begin to overlap.
  virtual bool ShouldCollide(b2Fixture* fixtureA, b2Fixture* fixtureB);
  
  /// Return true if contact calculations should be performed between a
  /// fixture and particle.  This is only called if the
  /// b2_fixtureContactListenerParticle flag is set on the particle.
  virtual bool ShouldCollide(b2Fixture* fixture,
                 b2ParticleSystem* particleSystem,
                 int32 particleIndex)
  {
    B2_NOT_USED(fixture);
    B2_NOT_USED(particleIndex);
    B2_NOT_USED(particleSystem);
    return true;
  }
  
  /// Return true if contact calculations should be performed between two
  /// particles.  This is only called if the
  /// b2_particleContactListenerParticle flag is set on the particle.
  virtual bool ShouldCollide(b2ParticleSystem* particleSystem,
                 int32 particleIndexA, int32 particleIndexB)
  {
    B2_NOT_USED(particleSystem);
    B2_NOT_USED(particleIndexA);
    B2_NOT_USED(particleIndexB);
    return true;
  }
};

/// Contact impulses for reporting. Impulses are used instead of forces because
/// sub-step forces may approach infinity for rigid body collisions. These
/// match up one-to-one with the contact points in b2Manifold.
struct B2_API b2ContactImpulse
{
  float normalImpulses[b2_maxManifoldPoints];
  float tangentImpulses[b2_maxManifoldPoints];
  int32 count;
};

/// Implement this class to get contact information. You can use these results for
/// things like sounds and game logic. You can also get contact results by
/// traversing the contact lists after the time step. However, you might miss
/// some contacts because continuous physics leads to sub-stepping.
/// Additionally you may receive multiple callbacks for the same contact in a
/// single time step.
/// You should strive to make your callbacks efficient because there may be
/// many callbacks per time step.
/// @warning You cannot create/destroy Box2D entities inside these callbacks.
class B2_API b2ContactListener
{
public:
  virtual ~b2ContactListener() {}

  /// Called when two fixtures begin to touch.
  virtual void BeginContact(b2Contact* contact) { B2_NOT_USED(contact); }

  /// Called when two fixtures cease to touch.
  virtual void EndContact(b2Contact* contact) { B2_NOT_USED(contact); }
  
  /// Called when a fixture and particle start touching if the
  /// b2_fixtureContactFilterParticle flag is set on the particle.
  virtual void BeginContact(b2ParticleSystem* particleSystem,
                b2ParticleBodyContact* particleBodyContact)
  {
    B2_NOT_USED(particleSystem);
    B2_NOT_USED(particleBodyContact);
  }

  /// Called when a fixture and particle stop touching if the
  /// b2_fixtureContactFilterParticle flag is set on the particle.
  virtual void EndContact(b2Fixture* fixture,
              b2ParticleSystem* particleSystem, int32 index)
  {
    B2_NOT_USED(fixture);
    B2_NOT_USED(particleSystem);
    B2_NOT_USED(index);
  }

  /// Called when two particles start touching if
  /// b2_particleContactFilterParticle flag is set on either particle.
  virtual void BeginContact(b2ParticleSystem* particleSystem,
                b2ParticleContact* particleContact)
  {
    B2_NOT_USED(particleSystem);
    B2_NOT_USED(particleContact);
  }

  /// Called when two particles start touching if
  /// b2_particleContactFilterParticle flag is set on either particle.
  virtual void EndContact(b2ParticleSystem* particleSystem,
              int32 indexA, int32 indexB)
  {
    B2_NOT_USED(particleSystem);
    B2_NOT_USED(indexA);
    B2_NOT_USED(indexB);
  }
  
  /// This is called after a contact is updated. This allows you to inspect a
  /// contact before it goes to the solver. If you are careful, you can modify the
  /// contact manifold (e.g. disable contact).
  /// A copy of the old manifold is provided so that you can detect changes.
  /// Note: this is called only for awake bodies.
  /// Note: this is called even when the number of contact points is zero.
  /// Note: this is not called for sensors.
  /// Note: if you set the number of contact points to zero, you will not
  /// get an EndContact callback. However, you may get a BeginContact callback
  /// the next step.
  virtual void PreSolve(b2Contact* contact, const b2Manifold* oldManifold)
  {
    B2_NOT_USED(contact);
    B2_NOT_USED(oldManifold);
  }

  /// This lets you inspect a contact after the solver is finished. This is useful
  /// for inspecting impulses.
  /// Note: the contact manifold does not include time of impact impulses, which can be
  /// arbitrarily large if the sub-step is small. Hence the impulse is provided explicitly
  /// in a separate data structure.
  /// Note: this is only called for contacts that are touching, solid, and awake.
  virtual void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse)
  {
    B2_NOT_USED(contact);
    B2_NOT_USED(impulse);
  }
};

/// Callback class for AABB queries.
/// See b2World::Query
class B2_API b2QueryCallback
{
public:
  virtual ~b2QueryCallback() {}

  /// Called for each fixture found in the query AABB.
  /// @return false to terminate the query.
  virtual bool ReportFixture(b2Fixture* fixture) = 0;
  
  /// Called for each particle found in the query AABB.
  /// @return false to terminate the query.
  virtual bool ReportParticle(const b2ParticleSystem* particleSystem,
                int32 index)
  {
    B2_NOT_USED(particleSystem);
    B2_NOT_USED(index);
    return false;
  }

  /// Cull an entire particle system from b2World::QueryAABB. Ignored for
  /// b2ParticleSystem::QueryAABB.
  /// @return true if you want to include particleSystem in the AABB query,
  /// or false to cull particleSystem from the AABB query.
  virtual bool ShouldQueryParticleSystem(
    const b2ParticleSystem* particleSystem)
  {
    B2_NOT_USED(particleSystem);
    return true;
  }
};

/// Callback class for ray casts.
/// See b2World::RayCast
class B2_API b2RayCastCallback
{
public:
  virtual ~b2RayCastCallback() {}

  /// Called for each fixture found in the query. You control how the ray cast
  /// proceeds by returning a float:
  /// return -1: ignore this fixture and continue
  /// return 0: terminate the ray cast
  /// return fraction: clip the ray to this point
  /// return 1: don't clip the ray and continue
  /// @param fixture the fixture hit by the ray
  /// @param point the point of initial intersection
  /// @param normal the normal vector at the point of intersection
  /// @param fraction the fraction along the ray at the point of intersection
  /// @return -1 to filter, 0 to terminate, fraction to clip the ray for
  /// closest hit, 1 to continue
  virtual float ReportFixture(	b2Fixture* fixture, const b2Vec2& point,
                  const b2Vec2& normal, float fraction) = 0;
                  
  /// Called for each particle found in the query. You control how the ray
  /// cast proceeds by returning a float:
  /// return <=0: ignore the remaining particles in this particle system
  /// return fraction: ignore particles that are 'fraction' percent farther
  ///   along the line from 'point1' to 'point2'. Note that 'point1' and
  ///   'point2' are parameters to b2World::RayCast.
  /// @param particleSystem the particle system containing the particle
  /// @param index the index of the particle in particleSystem
  /// @param point the point of intersection bt the ray and the particle
  /// @param normal the normal vector at the point of intersection
  /// @param fraction percent (0.0~1.0) from 'point0' to 'point1' along the
  ///   ray. Note that 'point1' and 'point2' are parameters to
  ///   b2World::RayCast.
  /// @return <=0 to ignore rest of particle system, fraction to ignore
  /// particles that are farther away.
  virtual float32 ReportParticle(const b2ParticleSystem* particleSystem,
                   int32 index, const b2Vec2& point,
                   const b2Vec2& normal, float32 fraction)
  {
    B2_NOT_USED(particleSystem);
    B2_NOT_USED(index);
    B2_NOT_USED(&point);
    B2_NOT_USED(&normal);
    B2_NOT_USED(fraction);
    return 0;
  }

  /// Cull an entire particle system from b2World::RayCast. Ignored in
  /// b2ParticleSystem::RayCast.
  /// @return true if you want to include particleSystem in the RayCast, or
  /// false to cull particleSystem from the RayCast.
  virtual bool ShouldQueryParticleSystem(
    const b2ParticleSystem* particleSystem)
  {
    B2_NOT_USED(particleSystem);
    return true;
  }
};

#endif
